1. Technical Field
The present invention relates to an inertial sensor such as an acceleration sensor and a gyro sensor and a method for manufacturing it, and is particularly preferred for in-vehicle navigation devices.
2. Related Art
In-car navigation devices are popularly spread out. When detecting a current position of a vehicle via such device, two methods are combined: a method for positioning a vehicle by using a so-called global positioning system (GPS), and a method for autonomously positioning the moving direction and distance of a vehicle. In order to autonomously position the moving direction and distance of a vehicle, an inertial sensor such as a gyro sensor (an angular velocity sensor) for detecting acceleration or angular velocity yielded by a moving vehicle are mounted in car navigation devices.
When acceleration or angular velocity is detected by using an inertial sensor, the detection axis of the sensor needs to be coincided with a direction to be detected. For example, the detection axis of a gyro sensor needs to be installed upward along the vertical direction.
In recent years, downsizing in-car navigation devices have been advanced. A casing main body (hereinafter, referred to as “an navigation body”), has been developed as to be installed into a center console between a driver seat and a passenger seat, though it was conventionally installed under a seat or inside a trunk.
FIGS. 15A and 15B show a navigation body installed in a center console. FIG. 15A is the whole perspective view. FIG. 15B shows a gyro sensor mounted in the navigation body.
When a navigation body 100 is installed in a center console 102 as shown in FIG. 15A, the surface of a display 101 and an operation panel (not shown) are preferably directed to a driver's viewing direction because of his/her visibility of the display 101 and operability of the operation panel. That is, the navigation body 100 is preferably installed tilted obliquely upward from the horizontal direction in the center console 102. When the navigation body 100 is installed tilted obliquely upward in the center console 102, however, as shown in FIG. 15B, the detection axis G of a gyro sensor 104 is slanted by angle (a tilt angle) θ from the vertical direction V. Here, the gyro sensor 104 is mounted on a printed board 103 in the navigation body 100 that is installed with also tilted by the angle θ. Due to this tilt, errors occur in angular velocity detected by the gyro sensor 104.
In ordinal car navigation devices, such detection errors of the gyro sensor 104 due to the installation angle of the navigation body 100 are corrected by software arithmetic processing. The software arithmetic processing, however, is insufficient. For example, the software arithmetic processing cannot correct detection errors when the tilt angle θ of the navigation body 100 is 30° or more.
In order to avoid such insufficiency, an inertial sensor is required that can correctly perform a detection even when a car navigation device is installed tilted. Various kinds of sensors are proposed to satisfy the requirement.
For example, a first example of related art discloses an angular velocity sensor in which a detection axis is tilted by an angular velocity detection element inside the sensor being slanted from a holder without changing the shape of or mounting method of the sensor.
Further, a second example of related art discloses a sensor device provided with a detection element detecting a direction and magnitude of a physical quantity having a constant directional property and a fixture for fixing and supporting the detection element. In the device, the detection element is fixed to the fixture and tilted by a predetermined reduced angle in a reducing direction. The reducing direction reduces an predicted angular difference between the direction of the detection axis, serving as the reference for detecting the magnitude and the direction of the physical quantity, and a direction of the physical quantity actually applied to the detection element during detecting.
A third example of related art discloses a supporting structure in which the angle of a vibrator in a package is set by a support connecting the vibrator to a support substrate and an adhesive bonding the support substrate and a package substrate so as to direct the detection axis of the vibrator in a desired direction.
Here, WO03/100350 is the first example, JP-A-2003-227844 is the second example, and JP-A-2005-249428 is the third example of related art.
The sensors disclosed in the first and second examples, however, may deteriorate detection performance due to acoustic leakages or unwanted vibration modes of the quartz crystal resonator yielded from a fixture since the quartz crystal resonator serving as a detection element is directly fixed to the fixture.
In addition, the sensors disclosed in the first and second examples, a specialized tool is required for every fixing angle since the detection element in itself needs to be fixed tilted. As a result, production costs soar. The reason for requiring the specialized tool is as follows. In each sensor, the detection element is irradiated with a laser to adjust the sensor after fixing the detection element to the fixture. Thus, one of focal points of the laser differs from others every one of fixing angles when changing the fixing angle, resulting in that the same tool is not shared.
Further, in the second example, a slit is formed in a detection element in itself for fixing it tilted. This process causes a high cost of a detection element, increasing total production costs.
Furthermore, in the first and second examples the angle of a detection axis cannot be set to any angle when a sensor is mounted on a mount board since a detection element is set tilted within a sensor.
Further, a support (bonding wire) connecting a vibrating element (vibrator) to a support substrate shown in the third example significantly affects occurrence of acoustic leakages and unwanted vibration modes from the vibrating element, sometimes deteriorating detection performance of the sensor. In addition, changing the angle with using the adhesive causes large variations in production, resulting in a setting angle being inaccurate.
Further directly fixing an element to a fixture in the first and second examples also causes occurrence of acoustic leakages and unwanted vibration modes from the vibrating element, resulting in a setting angle being inaccurate.
Taking the above into consideration, the inventors pay attention to a method that a sensor device in which a sensor element is fixed by a conventional bonding method is bonded to a lead frame and molded. The method can suppress the occurrence of acoustic leakages and unwanted vibration modes since the sensor element is fixed by the conventional bonding method, control a setting angle corresponding to a detection axis, by which the sensor responds to movements, with the shape of the lead frame, and further secure mechanical strength as molded.
However, in the method, the sensor device including the sensor is tilted with respect to a mount surface corresponding to the detection axis by which the sensor responds to movements, by controlling the shape of the lead frame. Thus, when a sensor device is formed by using a related art molding method in which the outline of the molded one follows the outline of the sensor device, the outline of the sensor device is not parallel with the mount surface. This outline may worsen workability in mounting processes.